This is a note to let you know that I've just added the patch titled
tracing: Stop current tracer when resizing buffer
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-stop-current-tracer-when-resizing-buffer.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d78ab792705c7be1b91243b2544d1a79406a2ad7 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
Date: Tue, 5 Dec 2023 16:52:10 -0500
Subject: tracing: Stop current tracer when resizing buffer
From: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
commit d78ab792705c7be1b91243b2544d1a79406a2ad7 upstream.
When the ring buffer is being resized, it can cause side effects to the
running tracer. For instance, there's a race with irqsoff tracer that
swaps individual per cpu buffers between the main buffer and the snapshot
buffer. The resize operation modifies the main buffer and then the
snapshot buffer. If a swap happens in between those two operations it will
break the tracer.
Simply stop the running tracer before resizing the buffers and enable it
again when finished.
Link: https://lkml.kernel.org/r/20231205220010.748996423@xxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Fixes: 3928a8a2d9808 ("ftrace: make work with new ring buffer")
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6394,9 +6394,12 @@ static int __tracing_resize_ring_buffer(
if (!tr->array_buffer.buffer)
return 0;
+ /* Do not allow tracing while resizng ring buffer */
+ tracing_stop_tr(tr);
+
ret = ring_buffer_resize(tr->array_buffer.buffer, size, cpu);
if (ret < 0)
- return ret;
+ goto out_start;
#ifdef CONFIG_TRACER_MAX_TRACE
if (!tr->current_trace->use_max_tr)
@@ -6424,7 +6427,7 @@ static int __tracing_resize_ring_buffer(
WARN_ON(1);
tracing_disabled = 1;
}
- return ret;
+ goto out_start;
}
update_buffer_entries(&tr->max_buffer, cpu);
@@ -6433,7 +6436,8 @@ static int __tracing_resize_ring_buffer(
#endif /* CONFIG_TRACER_MAX_TRACE */
update_buffer_entries(&tr->array_buffer, cpu);
-
+ out_start:
+ tracing_start_tr(tr);
return ret;
}
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-6.6/tracing-fix-a-possible-race-when-disabling-buffered-events.patch
queue-6.6/ring-buffer-force-absolute-timestamp-on-discard-of-event.patch
queue-6.6/tracing-fix-incomplete-locking-when-disabling-buffered-events.patch
queue-6.6/tracing-stop-current-tracer-when-resizing-buffer.patch
queue-6.6/ring-buffer-test-last-update-in-32bit-version-of-__rb_time_read.patch
queue-6.6/tracing-fix-a-warning-when-allocating-buffered-event.patch
queue-6.6/tracing-disable-snapshot-buffer-when-stopping-instance-tracers.patch
queue-6.6/tracing-always-update-snapshot-buffer-size.patch
